Surveillance/Research Update

Background

Since the initiation of Alberta’s chronic wasting disease (CWD) surveillance program in 1996, two game-farmed cervids, a ranched elk at slaughter and a white-tailed deer that died on the farm have been diagnosed with CWD. Both animals were diagnosed in 2002. The detection of scrapie in an Alberta sheep, in the spring of 2003, was followed by the diagnosis of Canada’s first indigenous case of bovine spongiform encephalopathy (BSE) in an Alberta cow, in May 2003. The presumptive TSE positive diagnoses were made by Alberta Agriculture’s Food Safety Division (FSD), using prion-specific immunohistochemistry (IHC) staining.

In anticipation of increased BSE testing requirements in Alberta and Canada following the positive BSE diagnosis, and in order to reduce the turn-around-time of reporting TSE test results, the FSD developed an enhanced bio-containment level 2 TSE laboratory and selected the Bio-Rad TeSeE® enzyme-linked immunosorbent assay (ELISA) as the diagnostic test for rapid TSE screening. Development of the TSE rapid test laboratory, located in the O.S. Longman Laboratory, Edmonton, commenced in May 2003 and was completed by December 2003. The laboratory was audited and certified by the Canadian Food Inspection Agency (CFIA) in January 2004.

The Bio-Rad TeSeE® ELISA was chosen for several reasons. It has been validated and approved by the European Union (EU) for the diagnosis of BSE and is currently used in the United Kingdom (UK) and several European countries, as well as Japan, as the diagnostic test for high-throughput BSE screening programs. The BSE test results generated by countries that use the Bio-Rad TeSeE® ELISA should thus be readily accepted internationally by trading partners. In addition, the United States Department of Agriculture has validated and licensed the Bio-Rad TeSeE® ELISA for diagnosing CWD in deer and elk and it has recently been evaluated in the United Kingdom for diagnosing scrapie in sheep. The Bio-Rad TeSeE® ELISA thus has the potential to be used as the diagnostic test for BSE, CWD and scrapie surveillance. It has demonstrated high sensitivity, specificity and reliability for diagnosing TSEs and is readily automated using robotic work stations, thus allowing it to be used for low, medium or high-throughput testing. The cost of the test itself is reasonable ($19.00 for test materials only) and the time from sample preparation in the laboratory to when results are ready is about 7.5 hours. In house and Bio-Rad bar code recognition systems allow traceability of all samples throughout the testing procedure.

Bio-Rad training

Bio-Rad provides an intensive TeSeE® ELISA training program for technical and scientific personnel at their laboratory in Marnes, France, in order to quality assure the reliability of the TeSeE® ELISA for diagnosing TSEs. However, equivalent training was provided for Agri-Food Laboratories Branch (AFLB) technical and scientific staff by Bio-Rad scientists and engineers at the CFIA National BSE and National CWD/Scrapie Reference Laboratories, as well as on-site during the set up of the TSE rapid test laboratory in Edmonton.

Evaluation of the Bio-Rad TeSeE® ELISA for diagnosing TSEs in Alberta

In order to satisfy CFIA quality assurance requirements and ISO 17025 accreditation requirements when laboratories plan to adopt a new diagnostic test, the FSD collaborated with the CFIA CWD/Scrapie Reference Laboratory and the Veterinary Diagnostic Laboratory at the University of Colorado in conducting inter-laboratory analytical and field studies to evaluate the sensitivity, specificity and reliability of the Bio-Rad TeSeE® ELISA for diagnosing CWD in elk and deer. The results of the evaluation studies were excellent. Similar inter-laboratory field evaluation studies for diagnosing BSE in cattle (FSD & CFIA BSE Reference Laboratory) and scrapie in sheep (FSD & CFIA CWD/Scrapie Reference Laboratory), using the Bio-Rad TeSeE® ELISA, are in progress and will be completed in early 2004. Manuscripts of the evaluation studies will be submitted for publication in a peer-reviewed scientific journal in 2004.

Commencement of TSE rapid testing by Alberta Agriculture, Food and Rural Development

Three additional laboratory technicians were hired in January 2004 to staff the TSE rapid test laboratory and were trained by the laboratory scientists of the Immunology/Virology Work Unit, AFLB. Testing surveillance cervids for CWD, using the Bio-Rad TeSeE® ELISA, began on February 5, 2004. During the last 2 weeks of February, 800 cervid samples were screened for CWD. There have been no ELISA positive reactors to date. Testing surveillance cattle for BSE, using the Bio-Rad TeSeE® ELISA, began on March 5, 2004.

Edmonton’s TSE rapid test laboratory is the first provincial laboratory to be certified by the CFIA to use the Bio-Rad TeSeE® ELISA as a diagnostic screening test for CWD and BSE surveillance. The Bio-Rad TeSeE® ELISA is currently the only rapid test approved by the CFIA for screening both cervids for CWD and cattle for BSE. The Edmonton laboratory currently has the highest testing capacity of any TSE laboratory in Canada.

TSE rapid testing capacity

Using the Bio-Rad TeSeE® ELISA, with automation, the Edmonton TSE rapid test laboratory has a current capacity of approximately 50,000 to 75,000 tests per year. With the current laboratory staff, enhancements to the database and further automation of the test procedure and specimen bar code system will allow a higher testing capacity, if required.

Turn-around-time for test results

Based on a 7.5 hour testing time, and the time required for thawing frozen samples, sampling, shipping samples from FSD regional laboratories to the Edmonton laboratory and reporting, the turn-around- time for the rapid test results is estimated to be 5 working days, from the time the specimen arrives at the laboratory until test results are reported.